Science & Fun - Jonathan Graehl

brain cell death (both neuronal and glial) is a process that begins at ~ 2 years of age – at least for the neurons that comprise the gray matter of the cerebral cortex, and which proceeds relentlessly throughout the individual’s lifetime (Giorgio, 2010) Brain cell loss and degeneration become morphologically apparent in the brain’s white matter by the time we are in our early 20’s, although there is evidence that more subtle changes have been afoot for much longer. (Hedden, 2004) Losses in gray matter volume proceed approximately linearly with age in normal aging, and the average gray matter volume decreases from ~390 mL at age 22, to ~300 ml at age 82. (Courchesne, 2000) Total loss in brain mass between age 20 and age 80 is, on average, ~450 g, or roughly 1/3^rd of our youthful brain volume.